Measurements of lift plates

ABSTRACT

An example apparatus includes a lift plate of a tray to hold a print medium. A support member is operatively connected to the lift plate. A sensor is attached to the support member to measure a distance of the lift plate from the sensor. A processor may receive a measurement of the distance of the lift plate from the sensor, and output an indicator describing an amount of print media in the tray based on the measurement of the distance of the lift plate from the sensor.

BACKGROUND

A printer or copier includes an input tray in which sheets of paper are stacked for feeding into the printer or copier. The input tray has a certain size that defines the capacity of printable media it will hold before the tray has to be refilled with additional paper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an apparatus to sense the status of a lift plate, according to an example.

FIG. 2 is a block diagram illustrating a communication device linked to the apparatus of FIG. 1, according to an example.

FIG. 3A is a block diagram illustrating a document management device linked to a communication device, according to an example.

FIG. 3B is a block diagram illustrating a document management device linked to a communication device, according to another example.

FIG. 4 is a perspective view illustrating a lift plate sensor device, according to an example.

FIG. 5 is a top perspective view illustrating the lift plate sensor device of FIG. 4, according to an example.

FIG. 6A is a side perspective view illustrating the lift plate sensor device of FIG. 4 in a first configuration, according to an example.

FIG. 6B is a side perspective view illustrating the lift plate sensor device of FIG. 4 in a second configuration, according to an example.

FIG. 7A is a side perspective view illustrating a lift plate sensor device in progressive configurations of the height of the lift plate, according to an example.

FIG. 7B is a side perspective view illustrating a lift plate sensor device in progressive configurations of the distance between the sensor and the lift plate, according to an example.

FIG. 8 is a sectional side view illustrating a document management device, according to an example.

FIG. 9A is a left side perspective view illustrating the lift plate sensor device of FIG. 4 connected to a support system, according to an example.

FIG. 9B is a right side perspective view illustrating the lift plate sensor device of FIG. 4 connected to a support system, according to an example.

FIG. 10 is a schematic diagram illustrating the lift plate sensor device of FIG. 4 interacting with a communication device, according to an example.

FIG. 11 is a block diagram illustrating a system to sense and report a status of a lift plate, according to an example.

DETAILED DESCRIPTION

For machines such as enterprise printers and copiers, users often have printing or copying jobs involving hundreds or maybe thousands of pages. The print medium input tray contains a restrictive number of sheets of printable media before additional media must be put into the tray by a user for continued printing/copying. This often requires a user to be constantly and visually monitoring the printing/copying process so that additional media may be placed in the tray when necessary. This constant monitoring may be a wasted use of the user's time. The examples described herein provide a sensor that detects the height of a lift plate carrying sheets of print media. As the stack of print media decreases; i.e., as the print media is fed into the printer/copier, the stack of print media decreases, and the lift plate rises, which reduces the distance between the sensor and the lift plate. The sensor uses this change/decrease in distance to indicate to a remote user operating a communication device how much print media is left in the tray. This data allows the remote user to monitor the status of the tray; i.e., how much print media remains in the tray and make arrangements; i.e., travel to the printer/copier to refill the tray or inform a user who is local to the printer, etc. to re-load the tray with additional print media without a long delay and thus reduce the amount of time that the tray stays empty. This is especially helpful for bulk print jobs requiring a near-constant supply of paper. This also eliminates the need for a local user to be constantly monitoring the printer to check when the tray is empty. Accordingly, the examples described herein provide a sensor that monitors the height of a lift plate of a printer and generates a qualitative indicator of the amount of paper remaining in the tray, and then reports the data to a remote user. As referred to herein, the term printable medium or media may refer to one or more sheets of paper or any other media suitable for insertion into a document management machine or device such as a printer, scanner, copier, or fax machine, etc.

An example provides an apparatus, for example a document management machine or device, including a lift plate of a tray to hold a print medium. A support member is operatively connected to the lift plate. A sensor is attached to the support member to measure a distance between the sensor and the lift plate. A processor is provided to receive a measurement of the distance of the lift plate from the sensor, and output an indicator describing an amount of print media in the tray based on the measurement of the distance of the lift plate from the sensor. The processor may also generate an object identifier value corresponding to the measurement of the distance between the sensor and the lift plate. The processor may further generate a qualitative description of an amount of print media in the tray based on the object identifier value. The processor may send any of the indicator, object identifier value, and the qualitative description to a communication device remotely-located from the tray. The object identifier value may correspond to an amount of print media in the tray as a function of an angle of rotation of the lift plate. The sensor may detect a time-of-flight laser that is directed substantially perpendicular to the lift plate. Furthermore, the sensor may include an infrared sensor. The sensor may calculate a height of the lift plate relative to a bottom of the tray based on the measured distance of the lift plate from the sensor. The distance between the sensor and the lift plate may decrease as an amount of print media in the tray decreases. The indicator may be any of a qualitative indicator and a quantitative indicator. Moreover, the indicator may correlate the amount of print media in the tray as a function of the angle of rotation of the lift plate.

Another example provides a method of remotely monitoring a status of a tray. The method may be stored in a machine-readable storage medium including instructions that when executed cause a processor of an electronic device to detect a print medium on a lift plate positioned in the tray, automatically measure an angle of rotation of the lift plate as an amount of print media decreases on the lift plate, generate an indicator that correlates the amount of print media in the tray as a function of the measurement of the angle of rotation of the lift plate, and transmit the indicator to a communication device that is remotely-located from the tray. The indicator may include an object identifier value corresponding to the measurement of the angle of rotation of the lift plate. The indicator may include a qualitative description of the amount of print media in the tray based on the measurement of the angle of rotation of the lift plate. The indicator may include a color-coded indicator.

FIG. 1 illustrates a block diagram illustrating an apparatus 10 including a lift plate 15 of a tray 20 to hold a print medium 25. The block diagram is not limited to the particular configuration presented in FIG. 1, and is provided merely as an example of the elements of the apparatus 10 arranged in a block diagram. The lift plate 15 may be configured as any suitable lift plate used in a tray 20 for holding a print medium 25, and may be used in any type of printing or copier device. The tray 20 may be any suitable tray or cartridge used in printers, copiers, scanners, and fax machines, or any other type of document management device which holds print medium for feeding into the machine. For ease of explanation, the term tray is used herein to describe any suitable tray or cartridge for any type of document management device.

The print medium 25 may be any type of print medium, as described above, and include any suitable feature including the size, shape, material, thickness, or any other quality suitable for placement in a tray 20 and suitable for being held by the lift plate 15. A support member 30 is operatively connected to the lift plate 15. The support member 30 may be configured in any suitable manner and positioned in any location relative to the lift plate 15. Moreover, the support member 30 may contain multiple components or arranged as part of a sub-system of components. The support member 30 includes suitable mechanical properties to withstand repetitive use of the lift plate 15 and any other mechanical, electrical, or chemical properties often experienced by a lift plate 15 or tray 20 installed and used in a printer or copier device. A sensor 35 is attached to the support member 30 to measure a distance D of the lift plate 15 from the sensor 35. In an example, the sensor 35 includes a time-of-flight sensor, which may calculate the distance D based on the known speed of light and utilizing a light signal or laser to project onto the lift plate 15 and measure the time it takes for the light signal or laser to travel from the sensor 35 to the lift plate 15 and back to the sensor 35 after reflecting off the lift plate 15. However, other types of sensors may be used in accordance with various examples of the apparatus 10. As used herein, the term laser refers to a concentrated and amplified beam of light projected by a light source.

A processor 40 is provided to receive a measurement of the distance D of the lift plate 15 from the sensor 35, and output an indicator 45 describing an amount of print media 25 in the tray 20 based on the measurement of the distance D of the lift plate 15 from the sensor 35. The connection between the sensor 35 and the processor 40 may be a wired or wireless connection. In various examples, the processor 40 may include a microprocessor, an application-specific integrated circuit (ASIC) processor, a digital signal processor, a networking processor, a multi-core processor, or other suitable processors selected to be communicatively linked to the sensor 35. In an example, the indicator 45 may be either a quantitative indicator providing a count or estimate of the amount of print media 25 remaining in the tray 20, or a qualitative indicator in the form of descriptions about the status of the lift plate 15 including a qualitative description of the amount of print media 25 remaining on the lift plate 15 and in the tray 20, the time remaining until the print media 25 will be fully exhausted and additional print media 25 will have to be added to the tray 20, the relative position of the lift tray 20 within the tray 20, a category of the amount of print media 25 remaining in the tray 20, among other types of descriptions about the status of the lift plate 15 and/or tray 20. In an example, a qualitative description of the amount of print media 25 remaining in the tray 20 may be Very Low, Low, Half, High, Full, etc. or any other type of qualitative and/or quantitative descriptor of the amount of print media 25 in the tray 20. For example, a qualitative and/or quantitative output may include a percentage or the number of sheets of print media 25 left in the tray 20. Moreover, these outputs may be broken up into as many levels as desired. Accordingly, the examples described herein are not limited to any specific number of tray status outputs.

FIG. 2, with reference to FIG. 1, is a block diagram illustrating a communication device 50 linked to the apparatus 10, according to an example. The processor 40 may send the indicator 45 to a communication device 50 that is remotely-located from the tray 20. The communication device 50 may be a computer, tablet, smartphone, wearable device, or any other type of electronic device having the capability to output the indicator 45 for a user in the form of an audio output or a visual output, or a combination of both.

The communication device 50 may be linked to the processor 50 through a wired connection or through a wireless connection over a communication network. The communication device 50 may be configured to be run as a computer application program, e.g., an app, to provide the indicator 45 in a user-friendly and easily-accessible format to permit a user to be apprised of the status of the lift plate 15 and/or tray 20 at any time. Updates to the computer application program may be administered by the processor 40, in one example, or may be administered by another source either stored on the communication device 50 or elsewhere. The processor 40 may receive updates in the form of automatic firmware updates or downloadable software updates, which may be further updated to the communication device 50, according to an example, and which may be installed or updated by the communication device 50, according to another example.

In an example, the sensor 35 may detect a time-of-flight laser 55 that is directed substantially perpendicular to the lift plate 15. In this example, a laser 55 including light waves is directed towards the lift plate 15 and the sensor 35 calculates the transceiving time for sending and returning the light waves bouncing back from the lift plate 15 to the sensor 35. The laser 55 may comprise a substantially conical shape that progressively enlarges the further it travels away from the sensor 35. Accordingly, the sensor 35 calculates the total time for transmission of the laser 55 and receipt of the bounce-back of the laser 55 and transmits the data to the processor 40. The transceiving time for sending/receiving the laser 55 is a function of the height H of the lift plate 15, and accordingly the sensor 35 is able to measure the height H of the lift plate 15 based on the measured transceiving time. In order to generate as accurate a measurement as possible, no intervening components are positioned in between the pathway between the sensor 35 and the lift plate 15 for transceiving the laser 55. Moreover, the sensor 35 is positioned near the laser source 54, which is shown in FIGS. 4, 6A, and 6B, which directs the laser 55 in a substantially perpendicular path to the lift plate 15 in order to generate the most accurate measurement of the time for sending/receiving the laser 55 to/from the lift plate 15. In this regard, the sensor 35 may be positioned substantially parallel to the lift plate 15, and the laser source 54 directs the laser 55 to be substantially perpendicular to the lift plate 15.

In another example, the processor 40 is able to utilize the measured transceiving time to calculate the height H of the lift plate 15 itself without requiring the sensor 35 to perform the calculation. Furthermore, other types of lasers 55 may be utilized to allow the sensor 35 to measure the height H of the lift plate 15. According to another example, the sensor 35 may detect a distance D between the sensor 35 and the lift plate 15 based on the measured transceiving time for sending/receiving the laser 55 to/from the lift plate 15. The distance D and the height H are inversely related to one another in that as the height H of the lift plate 15 increases, the distance D between the sensor 35 and the lift plate 15 decreases. Similarly, as the height Hof the lift plate 15 decreases, the distance D between the sensor 35 and the lift plate 15 increases. According to an example, the sensor 35 may calculate the height H of the lift plate 15 relative to a bottom 21 of the tray 20 based on the measured distance D of the lift plate 15 from the sensor 35. In an example, the distance D between the sensor 35 and the lift plate 15 may decrease as the amount of print media 25 in the tray 20 decreases. The indicator 45 may correlate the amount of print media 25 in the tray 20 as a function of an angle of rotation θ of the lift plate 15.

FIGS. 3A and 3B, with reference to FIGS. 1 and 2, are block diagrams illustrating a document management device 60 linked to a communication device 50, according to various examples. The document management device 60 includes a tray 20, a lift plate 15 in the tray 20 to hold a print medium 25, a sensor 35 to measure a distance D between the sensor 35 and the lift plate 15, and a processor 40 to receive a measurement of the distance D between the sensor 35 and the lift plate 15, and generate an object identifier value 65 corresponding to the measurement of the distance D between the sensor 35 and the lift plate 15.

When print media 25 is inserted into a tray 20, it rests on the lift plate 15. The more print media 25, the greater the force exerted on the lift plate 15 causing the lift plate 15 to be lowered in the tray 20. A full stack of print media 25 may cause the lift plate 15 to be completely lowered in the tray 20 and resting in a substantially parallel alignment compared with the tray 20 itself. As print media 25 are fed into the document management device 60 for printing or copying, etc., the amount of print media 25 remaining in the tray 20 decreases, which decreases the amount of force being exerted on lift plate 15, which allows the lift plate 15 to rise upwards in the tray 20. The rising action of the lift plate 15 as the amount of print media 25 decreases is representative of the change in height H of the lift plate 15 such that the more print media 25 that is on the lift plate 15, the lower/smaller the height H, and conversely the less print media 25 that is on the lift plate 15, the higher/greater the height H. Because the height H of the lift plate 15 and the distance D between the sensor 35 and the lift plate 15 are inversely proportional, there is a rising action of the lift plate 15 as the amount of print media 25 decreases, which is representative of the change in distance D between the sensor 35 and the lift plate 15 such that the less print media 25 that is on the lift plate 15, the less/smaller the distance D, and conversely the more print media 25 that is on the lift plate 15, the more/greater the distance D.

In FIG. 3A, the processor 40 is depicted as part of the document management device 60. In FIG. 3B, the processor 40 is depicted as being operatively linked to, but not necessarily part of, the document management device 60. Accordingly, as described above, the sensor 35 and the processor 40 may be wired or wirelessly linked to one another. In a wireless connection, the processor 40 may be configured in a separate device including the communication device 50 or may be part of a server device, not shown, communicating with linked devices, such as the communication device 50 or the document management device 60 in a client/server relationship and, in one example, through a cloud computing environment.

The processor 40 may generate a qualitative description 70 of the amount of print media 25 in the tray 20 based on the object identifier value 65. The processor 40 may send any of the object identifier value 65 and the qualitative description 70 to the communication device 50 remotely-located from the tray 20. In an example, the object identifier value 65 corresponds to the amount of print media 25 in the tray 20 as a function of the angle θ of rotation of the lift plate 15. In another example, the qualitative description 70 may provide the status of the lift plate 15 including the amount of printable media remaining on the lift plate 15 and in the tray 20, the time remaining until the print media 25 will be fully exhausted and additional print media 25 will have to be added to the tray 20, the relative position of the lift plate 15 within the tray 20, a category of the amount of print media 25 remaining in the tray 20, among other types of descriptions about the status of the lift plate 15 and/or tray 20. In this regard, the qualitative description 70 is analogous to the indicator 45 described above with reference to FIGS. 1 and 2, and may provide more explanation with respect to the status of the lift plate 15 compared with the qualitative indicator 45. In one example, the qualitative indicator 45 may be a numeric representation of the status of the lift plate 15 including an estimate of the number of print media 25 remaining in the tray 20, whereas the qualitative description 70 may provide a non-numeric descriptive explanation of the status of the lift plate 15 including the amount of print media 25 remaining in the tray 20.

The object identifier value 65 may be an output reading generated by the sensor 35 and output by the processor 40 providing the status of the amount of print media 25 remaining on the lift plate 15 in the tray 20. The object identifier value 65 may be a binary output providing only numeric readings or it may be a qualitative description of the status of the lift plate 15 and the amount of print media 25 remaining in the tray 20. In an example, the object identifier value 65 may provide a range of the amount of print media 25 remaining in the tray 20. The object identifier value 65 may be combined with any of the indicator 45 and qualitative description 70 to be output or displayed by the communication device 50. Furthermore, any of the indicator 45, object identifier value 65, and qualitative description 70 may be color-coded and may be visually displayed by the communication device 50 in any color, shape, or visual format, according to an example.

As described above, a time-of-flight laser 55 is directed substantially perpendicular to the lift plate 15. In another example, the sensor 35 may include an infrared sensor 35 utilizing the transmission of infrared waves for measuring the distance D between the sensor 35 and the lift plate 15, or for measuring the height H of the lift plate 15. In other examples, the sensor 35 may be configured as any suitable detector capable of measuring the amount of print media 25 remaining in the tray 20.

FIG. 4, with reference to FIGS. 1 through 3B, is a perspective view illustrating a lift plate sensor device 100, according to an example. The lift plate sensor device 100 may include the lift plate 15, which is configured to hold print media 25, which is not shown in FIG. 4. The lift plate 15 includes a first side 16 and an oppositely positioned second side 17 such that the first side 16 is set to hold the print media 25. A pick idler roller 90 is positioned around a pick idler shaft 85 at a first end 91 of the lift plate 15, and the pick idler roller 90 is biased against the lift plate 15, and as print media 25 is fed into a document management device 60, the pick idler roller 90 rotates and grabs the upper most print medium 25 for insertion into the document management device 60. The lift plate sensor device 100 may further include a pair of rotating guides 95 positioned at a second end 92 of the lift plate 15. Print media 25 is set to be held on the first side 16 of the lift plate 15 within the width defined by the spacing between the pair of rotating guides 95 on the lift plate 15. A support arm 94 is positioned under the lift plate 15 adjacent to the second side 17 and connects to the pair of rotating guides 95. In an example, the pair of rotating guides 95 rotate as the lift plate 15 rises such that both rotating guides 95 rotate at a same rate and position as one another.

The lift plate sensor device 100 further includes the support member 30 above the first side 16, which may be operatively connected to the pick idler shaft 85. The support member 30 includes the sensor 35 held therein in a stable manner to provide support for the sensor 35. An offset arm 80 is positioned below the second side 17 of the lift plate 15. The offset arm 80 includes a width greater than the width of the lift plate 15 such that it is offset or exposed when viewed from above the lift plate 15. The sensor 35 and laser source 54 are positioned in the support member 30 to be substantially aligned with the offset arm 80 such that the exposed portion 81 of the offset arm 80 is in a direct path of the sensor 35 and laser source 54. In an example, the sensor 35 and laser source 54 are positioned substantially parallel to the exposed portion 81 of the offset arm 80. The laser source 54 directs the laser 55, if configured as a time-of-flight sensor, or other such infrared signal down to the exposed portion 81 of the offset arm 80 such that the laser 55 is substantially perpendicular to the offset arm 80. The sensor 35 measures the time it takes for the laser 55 to be transmitted to, and reflected from, the offset arm 80 back to the sensor 35. The transceiving time is a function of the height H of the lift plate 15 and the distance D between the sensor 35 and the lift plate 15, and more particularly, the distance D between the sensor 35 and the offset arm 80 of the lift plate 15, as previously described above. While the lift plate sensor device 100 is shown to include only one support member 30 with a corresponding sensor 35, other examples may provide for a pair of support members 30 positioned on either end of the pick idler shaft 85. Having a dual sensor system may enhance the measurement of the height H and distance D calculations and may act as a back-up/reserve system in case one of the sensors becomes disabled and/or non-functioning.

FIG. 5, with reference to FIGS. 1 through 4, is a top perspective view illustrating the lift plate sensor device 100 of FIG. 4, according to an example. As shown, the support member 30 is similarly offset from the lift plate 15 in the same manner as the offset arm 80. The sensor 35 is configured to fit in the support member 30 without requiring substantial mechanical support. However, a clear path between the sensor 35 and laser source 54 and the underlying exposed portion 81 of the offset arm 80 is provided to allow a clear path for the laser 55 to hit the offset arm 80 and for the sensor 35 to detect the laser 55. If the sensor 35 requires wired connections for power or communication with the processor 40, then the support member 30 may include appropriate wire leads or connectors to connect to the sensor 35.

FIGS. 6A and 6B, with reference to FIGS. 1 through 5, are side perspective views illustrating the lift plate sensor device 100 of FIG. 4 in a first and second configuration, respectively, according to an example. In FIG. 6A, the lift plate 15 is shown with print media 25 stacked at a thickness T_(A). In an example, thickness T_(A) may represent a full stack of the print media 25 on the lift plate 15. The pick idler roller 90 rests against the top of the print media 25, and the sensor 35, which is attached to the support member 30, is aligned with the offset arm 80 and a laser source 54 directs the laser 55 onto the offset arm 80. The distance D_(A) between the sensor 35 and the offset arm 80 of the lift plate 15 is measured by the sensor 35. The distance DA corresponds to the height H_(A) of the lift plate 15 with respect to the tray 20, which is not shown in FIG. 6A. Given the thickness T_(A) of the stack of print media 25 and the corresponding force exerted on the lift plate 15, the lift plate 15 creates a relatively small angle θ_(A) of rotation.

Similarly, in FIG. 6B, the lift plate 15 is shown with print media 25 stacked at a thickness T_(B). In an example, thickness T_(B) may represent a low stack of the print media 25 on the lift plate 15. The pick idler roller 90 rests against the top of the print media 25, and the sensor 35, which is attached to the support member 30, is aligned with the offset arm 80 and the laser source 54 directs the laser 55 onto the offset arm 80. The distance D_(B) between the sensor 35 and the offset arm 80 of the lift plate 15 is measured by the sensor 35. The distance D_(B) corresponds to the height H_(B) of the lift plate 15 with respect to the tray 20, which is not shown in FIG. 6B. Given the thickness T_(B) of the stack of print media 25 and the corresponding force exerted on the lift plate 15, the lift plate 15 creates a relatively large angle θ_(B) of rotation. More particularly, the angle θ_(B) of rotation is greater than the angle θ_(A) of rotation of the lift plate 15. Furthermore, as the lift plate 15 rises, the pair of rotating guides 95 rotate causing the lift plate 15 to also rotate. Accordingly, there is a direct correlation between the height of the lift plate 15 and the angle of rotation of the lift plate 15. In this regard, as the height H of the lift plate 15 increases, the angle θ of rotation of the lift plate 15 also increases. Moreover, as the height H and angle θ of rotation of the lift plate 15 increase, the distance D between the sensor 35 and the offset arm 80 of the lift plate 15 decreases.

FIG. 7A, with reference to FIGS. 1 through 6B, is a side perspective view illustrating a lift plate sensor device 100 in progressive configurations of the height of the lift plate 15, according to an example. As indicated in FIG. 7A, the lift plate 15 corresponding to height H₁ corresponds to a lift plate 15 that is substantially parallel to the tray 20, and corresponds to an angle θ₁, which is substantially 0° and represents the lift plate 15 carrying a substantially full stack of print media 25. As the print media 25 are continuously fed into the document management device 60 and the stack of print media 25 decreases, the lift plate 15 rises in the tray 20. The lift plate 15 corresponding to height H₂ corresponds to a lift plate 15 that is slightly angled with respect to the tray 20, and corresponds to an angle θ₂ and represents the lift plate 15 carrying a slightly less than full stack of print media 25. As additional print media 25 are fed into the document management device 60 and the stack of print media 25 continues to decrease, the lift plate 15 continues to rise in the tray 20. The lift plate 15 corresponding to height H₃ corresponds to a lift plate 15 that is significantly angled with respect to the tray 20, and corresponds to an angle θ₃ and represents the lift plate 15 carrying a slightly empty stack of print media 25. As the full stack of print media 25 is fed into the document management device 60 and no additional media 25 remains on the lift plate 15, the lift plate 15 rises to its greatest height H₄, which corresponds to the greatest angle θ₄ and represents the lift plate 15 carrying no print media 25. Accordingly, in FIG. 7B, H₁<H₂<H₃<H₄ and θ₁<θ₂<θ₃<θ₄.

FIG. 7B, with reference to FIGS. 1 through 7A, is a side perspective view illustrating a lift plate sensor device 100 in progressive configurations of the distance between the sensor 35 and the lift plate 15, according to an example. As indicated in FIG. 7B, as the lift plate 15 rises due to the decrease in print media 25 on the lift plate 15, the distance between the sensor 35 and lift plate 15 decreases. The lift plate 15 corresponding to distance D₁ corresponds to a lift plate 15 that is substantially parallel to the tray 20, and corresponds to an angle θ₁, which is substantially 0° and represents the lift plate 15 carrying a substantially full stack of print media 25. As the print media 25 are continuously fed into a document management device 60, which is not shown in FIG. 7B, and the stack of print media 25 decreases, the lift plate 15 rises. The lift plate 15 corresponding to distance D₂ corresponds to a lift plate 15 that is slightly angled, and corresponds to an angle θ₂ and represents the lift plate 15 carrying a slightly less than full stack of print media 25. As additional print media 25 are fed into the document management device 60 and the stack of print media 25 continues to decrease, the lift plate 15 continues to rise. The lift plate 15 corresponding to distance D₃ corresponds to a lift plate 15 that is significantly angled, and corresponds to an angle θ₃ and represents the lift plate 15 carrying a slightly empty stack of print media 25. As the full stack of print media 25 is fed into the document management device 60 and no additional media 25 remains on the lift plate 15, the lift plate 15 rises to its smallest distance D₄ between the sensor 35 and the lift plate 15, which corresponds to the greatest angle θ₄ and represents the lift plate 15 carrying no print media 25. Accordingly, in FIG. 7B, D₁>D₂>D₃>D₄ and θ₁<θ₂<θ₃<θ₄.

According to the examples described herein, the sensor 35 may utilize different measurements to determine the position of the lift plate 15. In one example, the sensor 35 may measure the distance D between the lift plate 15 and the sensor 35 using the laser 55 and a time-of-fight detection scheme. The processor 40 may be programmed with a corresponding set of instructions that automatically align the measured distance D to a corresponding indicator 45, object identifier value 65, and/or qualitative description 70 relative to the status of the amount of media 25 on the lift plate 15 in the tray 20. In another example, the sensor 35 may measure the height Hof the lift plate 15 by either detecting the position of the lift plate 15 relative to the bottom of the tray 20 or to detect the angle θ of rotation of the lift plate 15. The processor 40 may be programmed with a corresponding set of instructions that automatically align the measured height H or angle θ of rotation of the lift plate 15 to a corresponding indicator 45, object identifier value 65, and/or qualitative description 70 relative to the status of the amount of media 25 on the lift plate 15 in the tray 20. In another example, the sensor 35 may detect the distance D between the lift plate 15 and the sensor 35 using the laser 55 and any of the sensor 35 and the processor 40 may be programmed with a corresponding set of instructions that automatically align the distance D to a correspond pre-programmed height H. For example, the sensor 35 may be programmed to set the lowest height of the lift plate 15 at 0 mm and any upward movement or rotation of the lift plate 15 detected by the sensor 35 is automatically assigned a height based on the difference in the transceiving time of the laser 55, as described above.

FIG. 8, with reference to FIGS. 1 through 7B, is a sectional side view illustrating a document management device 60, according to an example. The positioning of the lift plate 15 relative to the tray 20 is depicted. The lift plate sensor device 100 is illustrated within the dotted oval. Additionally, the processor 40 is shown communicatively linked to the sensor 35. The relative position of the processor 40 within the document management device 60 in FIG. 8 is only an example, and accordingly the processor 40 may be positioned in any suitable location in the document management device 60. Furthermore, as described in an earlier example, the processor 40 may not be positioned in the document management device 60 at all, and may instead be part of another electronic device including the communication device 50. As such, the link from the processor 40 to the sensor 35 may be wired or wireless. The tray 20 with the connected lift plate 15 may be removable from the document management device 60 for inserting additional print media 25 as required.

FIGS. 9A and 9B are left side and right side perspective views, respectively, illustrating the lift plate sensor device 100 of FIG. 4 connected to a support system 105, according to an example. The lift plate sensor device 100 may be held in position in the tray 20 using the support system 105. In an example, the support system 105 includes a lever 110 coupled to a lift spring 115, which is coupled to a motor rack 120 including a rack and pinion system 125. The support system 105 is coupled to the support arm 94 that is positioned under the lift plate 15 and which connects to the pair of rotating guides 95. The motor rack 120 and rack and pinion system 125 assist in driving the rotation of the lift plate 15 as the stack of print media 25 reduces. Moreover, the spring 115 biases the lever 110 which raises the lift plate 15 as the stack of print media 25 reduces.

FIG. 10, with reference to FIGS. 1 through 9B, is a schematic diagram illustrating lift plate sensor devices 100 a-100 c interacting with a communication device 50, according to an example. As illustrated in the example of FIG. 10, three states of configuration correspond with the lift plate sensor devices 100 a-100 c, respectively. However, the examples described herein are not limited to any specific number of states of configuration of the lift plate sensor devices 100 a-100 c. In lift plate sensor device 100 a, there is no print media 25; e.g., 0 mm thick stack of print media 25, on the lift plate 15. In lift plate sensor device 100 b, there is a 4 mm thick stack of print media 25 on the lift plate 15. In lift plate sensor device 100 c, there is a 10 mm thick stack of print media 25 on the lift plate 15. Accordingly, the sensor 35 measures the corresponding height H, distance D, or angle θ of rotation with respect to the lift plate 15 and transmits the data measurement to the processor 40, which matches the data measurement to a pre-programmed list to a corresponding indicator 45, object identifier value 65, and/or qualitative description 70 relative to the status of the amount of media 25 on the lift plate 15 in the tray 20. For example, the object identifier value 65 may provide the thickness T of the print media 25 on the lift plate 15. For the lift plate sensor device 100 a, the object identifier value 65 may indicate that the thickness T of the print media 25 in the tray 20 is 0 mm≤T≤4 mm. For the lift plate sensor device 100 b, the object identifier value 65 may indicate that the thickness T of the print media 25 in the tray 20 is 4 mm<T≤10 mm. For the lift plate sensor device 100 c, the object identifier value 65 may indicate that the thickness T of the print media 25 in the tray 20 is T>10 mm. The object identifier value 65 may be transformed into the indicator 45 and/or qualitative description 70 for output on the communication device 50. Alternatively, the object identifier 65 may be output on the communication device 50 without being transformed into the indicator 45 and/or qualitative description 70. In an example, the indicator 45 may indicate that the object identifier data, OID, output is 0, which corresponds to the thickness T of the stack of print media 25 being 0 mm≤T≤4 mm, which may further correspond to a qualitative description 70 for this OID output indicating that the tray status is Very Low. In another example, the indicator 45 may indicate that the object identifier data, OID, output is 10, which corresponds to the thickness T of the stack of print media 25 being 4 mm<T≤10 mm, which may further correspond to a qualitative description 70 for this OID output indicating that the tray status is Low. According to another example, the indicator 45 may indicate that the object identifier data, OID, output is 100, which corresponds to the thickness T of the stack of print media 25 being T>10 mm, which may further correspond to a qualitative description 70 for this OID output indicating that the tray status is Full. Additionally, the indicator 45, object identifier value 65, and/or qualitative description 70 may be a color-coded indicator 75 to provide an enhanced visual indication on the communication device 50 as to the status of the lift plate 15 and the amount of print media 25 remaining in the tray 20. For example, a tray 20 with a relatively full stack of print media 25 may be represented by a green color indicator 75, a tray 20 with a half full stack of print media 25 may be represented by a yellow color indicator 75, and a tray with a relatively empty stack of print media 25 may be represented by a red color indicator 75. Because the communication device 50 is remotely-located from the lift plate sensor devices 100 a-100 c, a user does not have to be physically located near the document management device 60 to monitor the status of the amount of print media 25 remaining in the tray 20. In this regard, the user may be remotely-located and may receive an alert on the communication device 50 as to the status of the amount of print media 25 remaining in the tray 20 and as the amount of print media 25 becomes reduced, the user may determine when to go to the document management device 60 and insert additional print media 25 in the tray 20.

In another example, the indicator 45 may provide a time remaining until the print media 25 has been completely exhausted in the tray 20, which further provides a user with an indication of when additional print media 25 must be inserted into the tray 20. Another example provides a postponement feature such that if a print or copy job is sent to the document management device 60 that will take more print media 25 than the sensor 35 detects are in the tray 20, the document management device 60 may postpone the print/copy job or alert the user on the communication device 50 that there is insufficient print media 25 in the tray to accommodate the requested print/copy job. Conventional print/copy behavior would be to print/copy using the available print media 25 until they tray 20 runs out of the print media 25 and wait to print/copy the rest of the job when they tray 20 is refilled. However, the postponement feature provided by the example herein would be useful for secure print/copy jobs where it would be undesirable to have only a partial print/copy job sitting in the output bin of the document management device 60 waiting for the tray 20 to be refilled.

Various examples described herein may include both hardware and software elements. The examples that are implemented in software may include firmware, resident software, microcode, etc. Other examples may include a computer program product configured to include a pre-configured set of instructions, which when performed, may result in actions as stated in conjunction with the methods described above. In an example, the preconfigured set of instructions may be stored on a tangible non-transitory computer readable medium or a program storage device containing software code.

FIG. 11 with reference to FIGS. 1 through 10, is a block diagram of an electronic device 150 for monitoring the status of a tray 20, according to an example. The electronic device 150 may be the communication device 50, as described above, in one example. The electronic device 160 may be any other electronic device with signal processing capability, according to another example. In the example of FIG. 11, the electronic device 150 includes the processor 40 as described above and a machine-readable storage medium 155.

Processor 40 may include a central processing unit, microprocessors, and/or other hardware devices suitable for retrieval and execution of instructions stored in a machine-readable storage medium 155. Processor 40 may fetch, decode, and execute computer-executable instructions 162, 164, 166, and 168 to enable execution of locally-hosted or remotely-hosted applications for controlling action of the electronic device 150. The remotely-hosted applications may be accessible on one or more remotely-located devices, for example. As an alternative or in addition to retrieving and executing instructions, processor 40 may include one or more electronic circuits including a number of electronic components for performing the functionality of one or more of instructions 162, 164, 166, and 168.

The machine-readable storage medium 155 may be any electronic, magnetic, optical, or other physical storage device that stores executable instructions. Thus, the machine-readable storage medium 185 may be, for example, Random Access Memory, an Electrically-Erasable Programmable Read-Only Memory, a storage drive, an optical disc, and the like. In one example, the machine-readable storage medium 155 may include a non-transitory computer-readable storage medium. The machine-readable storage medium 155 may be encoded with executable instructions for enabling execution of remotely-hosted applications accessed on the one or more remotely-located devices.

In an example, the processor 65 of the electronic device 5 executes computer readable instructions. For example, computer-executable detecting instructions 162 may detect a print medium 25 on a lift plate 15 positioned in the tray 20. Computer-executable measuring instructions 164 may automatically measure an angle θ of rotation of the lift plate 15 as an amount of print media 25 decreases on the lift plate 15. Computer-executable generating instructions 166 may generate an indicator 45 that correlates the amount of print media 25 in the tray 20 as a function of the measurement of the angle θ of rotation of the lift plate 15. Computer-executable transmitting instructions 168 may transmit the indicator 45 to a communication device 50 that is remotely-located from the tray 20. As described above, the indicator 45 may include an object identifier value 65 corresponding to the measurement of the angle θ of rotation of the lift plate 15. The indicator 45 may include a qualitative description 70 of the amount of print media 25 in the tray 20 based on the measurement of the angle θ of rotation of the lift plate 15. The indicator 45 may include a color-coded indicator 75.

The present disclosure has been shown and described with reference to the foregoing exemplary implementations. Although specific examples have been illustrated and described herein it is manifestly intended that the scope of the claimed subject matter be limited only by the following claims and equivalents thereof. It is to be understood, however, that other forms, details, and examples may be made without departing from the spirit and scope of the disclosure that is defined in the following claims. 

What is claimed is:
 1. An apparatus comprising: a lift plate of a tray to hold a print medium; a support member operatively connected to the lift plate; a sensor attached to the support member to measure a distance of the lift plate from the sensor; and a processor to: receive a measurement of the distance of the lift plate from the sensor; and output an indicator describing an amount of print media in the tray based on the measurement of the distance of the lift plate from the sensor.
 2. The apparatus of claim 1, wherein the processor is to send the indicator to a communication device remotely-located from the tray.
 3. The apparatus of claim 1, wherein the sensor is to detect a time-of-flight laser that is directed substantially perpendicular to the lift plate.
 4. The apparatus of claim 1, wherein the sensor is to calculate a height of the lift plate relative to a bottom of the tray based on the measured distance of the lift plate from the sensor.
 5. The apparatus of claim 1, wherein the distance between the sensor and the lift plate decreases as an amount of print media in the tray decreases.
 6. The apparatus of claim 1, wherein the indicator correlates the amount of print media in the tray as a function of an angle of rotation of the lift plate.
 7. A document management device comprising: a tray; a lift plate in the tray to hold a print medium; a sensor to measure a distance between the sensor and the lift plate; and a processor to: receive a measurement of the distance between the sensor and the lift plate; and generate an object identifier value corresponding to the measurement of the distance between the sensor and the lift plate.
 8. The document management device of claim 7, wherein the processor is to generate a qualitative description of an amount of print media in the tray based on the object identifier value.
 9. The document management device of claim 8, wherein the processor is to send any of the object identifier value and the qualitative description to a communication device remotely-located from the tray.
 10. The document management device of claim 7, wherein the object identifier value corresponds to an amount of print media in the tray as a function of an angle of rotation of the lift plate.
 11. The document management device of claim 7, wherein the sensor comprises an infrared sensor.
 12. A machine-readable storage medium comprising instructions that when executed cause a processor of an electronic device to: detect a print medium on a lift plate positioned in the tray; automatically measure an angle of rotation of the lift plate as an amount of print media decreases on the lift plate; generate an indicator that correlates the amount of print media in the tray as a function of the measurement of the angle of rotation of the lift plate; and transmit the indicator to a communication device that is remotely-located from the tray.
 13. The machine-readable storage medium of claim 12, wherein the indicator comprises an object identifier value corresponding to the measurement of the angle of rotation of the lift plate.
 14. The machine-readable storage medium of claim 12, wherein the indicator comprises a qualitative description of the amount of print media in the tray based on the measurement of the angle of rotation of the lift plate.
 15. The machine-readable storage medium of claim 12, wherein the indicator comprises a color-coded indicator. 